1. Field of the Invention
The invention is in the field of manufacturing micro-structured elements such as micro-optical elements or micro-optical systems. It also extends to Micro-Electro-Mechanical Systems (MEMS) and combined micro-optical and electronic and/or mechanical systems such as Micro-Opto-Electro-Mechanical Systems (MOEMS). More concretely, it deals with a method of replicating—for example by an embossing or molding process—an element into a micro-structured element, with a replication tool, and with a method of manufacturing a replication tool.
2. Description of the Related Art
Micro-optical elements have gained increasing importance. Micro-optical elements here are elements of any kind that rely on micro-optics. The term ‘micro-optical elements’ here includes systems comprising electronic and/or mechanical components, such as, for example, the MOEMS. Micro-optics, as opposed to conventional optics, is based on fine structures causing refraction and/or diffraction, the structures having characteristic depths/heights and often also widths of typically a few micrometers, for example of 0.5 μm-200 μm, preferably of between 1 μm and about 50 μm or between 1 μm and about 30 μm. In other words, the characteristic profile depths and the profile widths are of the order of a few wavelengths up to a few tens of wavelengths for refractive optics and of about one wavelength up to a few wavelengths for diffractive optics. As a rule of thumb, micro-optical elements have structures such that the phase relation of radiation present at different neighboring places on the structure is well-defined. This is opposed to classical, purely refractive optical elements, where the behavior of the radiation at different elements of the structure can be described in a geometrical optics picture. Micro-optical elements, thus, as opposed to classical optical elements (such as classical lenses, mirror elements etc.) can be regarded as having structures which are such that the wave nature of the light has to be taken into account and participates in the effect the micro-optical element has upon radiation.
For manufacturing state of the art Diffractive Optical Elements (DOEs; being an example of Micro-Optical Elements), different methods are known. A first method is the manufacturing of a resist pattern using conventional photostructuring or electron beam structuring techniques relying on masks or the like. The resist pattern is used as a diffractive element. A second method includes the forming of a resist pattern using one of the mentioned techniques and then etching the substrate such that a diffraction element having a desired blazed shape is produced.
Other methods, such as the one disclosed in JP-A-168601/1988 rely on etching including structuring an etching stopper layer with a photolithographic process.
All these state of the art methods have in common that they are not very suitable for mass production, since the manufacturing of every element involves a series of elaborate production steps.
Therefore, it is an objective of the invention to provide a method of forming a micro-structured element which is suitable for producing micro-optical elements and overcomes drawbacks of prior art manufacturing methods. It should provide a good definition of the 3D-structural features and their absolute dimensions and positions, even if the micro-structured element is large or if an array of micro-structured elements is manufactured.